Modern agricultural machinery is getting bigger and stronger – tyre manufacturers must constantly look for solutions that will allow this power to be transferred to the terrain in just the right way. With tractors, in particular, the aim is to transfer the engine power as efficiently as possible while minimizing soil compaction. The type of technology used in the construction of a tyre by a given manufacturer translates into its operational parameters. The durability of the tyre and the resistance to wear of a given compound, as well as technologies that help combine high operational qualities of tyres with their reduced wear during the drive up to the field via paved roads, are also important.
Of course, which technologies are used and the advantages of a given tyre have an impact on its market segment, and therefore also on the price. Fortunately, the offer is so wide that every farmer will find something for himself – regardless of whether he farms for his own needs or is a large agricultural entrepreneur. It is important to have tyres suitable for our needs – neither too advanced, if we do not intent to make use of its capabilities, or – even worse – too cheap, if our machines are modern and have been purchased with the intention of increasing the farm's efficiency.
So which factors should we consider when buying new tyres, having in mind many hours of work on a field? What to consider when choosing the right tyres for ourselves? There is only one answer – our conscious needs in the field work.
Structure of agricultural tyres
Let's start with the basics – there are two basic types of agricultural tyres available on the market: radial-ply and diagonal-ply tyres, which differ mainly in their internal structure. Diagonal-ply tyres have a multi-layered structure of the carcass with the cord placed at an acute angle in relation to the direction of rotation of the tyre. In contrast, radial-ply tyre’s carcass’ cord is perpendicular to the direction of rotation of the tyre.
What are the advantages and disadvantages of this? Diagonal tyres are cheaper and more resistant to mechanical damage. Unfortunately, they require quite high pressure to work properly, which translates into higher level of soil compaction and the inability to lower the pressure when working in the field. With too little air, the diagonal tyre begins to deform – the contact area with the ground decreases and therefore operating costs increase. Such tyres are intended for less demanding work or for smaller farms, where the scale of production will not allow for visible savings in operation. Radial tyres, on the other hand, have better adhesion to the ground and can operate with reduced pressure without causing much compaction of the soil. Thanks to modern technologies, they also ensure better driving parameters and lower rolling resistance, thanks to which the vehicle consumes less fuel. Compared to diagonal tyres, they are more expensive and have a lower resistance to damage, but they compensate for this with fuel savings and greater efficiency of field work, which is an important factor for medium and large farm owners.
– Agricultural tyres, which are purchased in modern farms for really strong and solid machines, must be able to work effectively for many years. It is worth to choose them basing not only on our budgets, but also on what work will be performed with a given tractor. Let’s remember top-class tyres will be useless if we do not regularly check their pressure. Inadequate level of this parameter will effectively shorten the life of each tyre. It is worth talking to an advisor at the sales point so that they can advise us on what tyre will be best for our machines and farms – said Piotr Sarnecki, Piotr Sarnecki, general director of the Polish Tyre Industry Association (PTIA).
The right pressure matters
As in all tyres, also in the agricultural type, the pressure has a significant impact on operation and fuel consumption. This parameter should be monitored before field works and adjusted to the given work, axle load, and the weight of the machine with which we are going to work. Tyre manufacturers' conversion tables or calculators will help us with that. The key is to keep this parameter at the correct level – the most common mistake made by operators is inflating the tyre to a level that is way too high. – We never want to inflate agricultural tyres to the value indicated on the side of the tyre – these are the maximum amounts to which a tyre can be safely inflated during its assembly – adds Piotr Sarnecki.
Safe operation with reduced tyre pressure, ensuring greater work efficiency and minimizing soil compaction is possible only with modern tyres adapted to such characteristics - i.e. with radial tyres. Switching to this type of tyres allows you to reduce fuel consumption by 3-12%, which significantly reduces the operating costs of the vehicle. Unlike the diagonal type, the deformation of the radial tyre proceeds in an appropriate and controlled manner, which results in an increase in the footprint area in the soil. This reduces soil compaction on which the machine moves – which is especially important for operators of heavy agricultural machinery.
Over the past few years, agricultural tyre manufacturers have successfully introduced two new categories of radial tyres to the market, namely IF and VF tyres. They allow the use of lower operating pressure, respectively by 20 and 40% compared to classic radial tyres. The right pressure for these tyres is set on the basis of the current wheel load – that makes it a lot easier for the user to avoid troublesome need to change the pressure after working in the field and before going on a paved road, on which the tractor moves at a much higher speed.
How to achieve the highest durability?
Tyres can be protected against excessive wear by monitoring the looseness of linkages and the wear of steering knuckle bearing. Their occurrence may be manifested by the incorrect inclination of the wheels relative to the ground, and, as a consequence, faster wear of the tyres, especially the front ones. Contrary to what one might expect, we have an impact on the durability of switch bearings – they wear out much faster when the suspension geometry is incorrectly set. Correctly set suspension geometry has a significant impact on the tyre's running rate, and its regular inspection promotes longer tyre life.
Studies have shown that after exceeding 50% of the wear of the pad assemblies, greatest decreases in traction forces appear, and the further exploitation of the tyre is associated with lowering the driving economy – both on the soft ground and on the paved surface. As a consequence, the slippage increases as well as the fuel consumption itself - which makes it impossible to continue working effectively in the field. The situation is similar in the case of an asphalt road – as a result of an increase in friction against the ground, the combustion level increases. Before buying tyres, it is essential to carefully check the properties of the selected tyre model.
 “Assessment of tyre tread protrusion wear in the aspect of farm tractors traction capacity”, Institute of Agricultural Engineering, Wroclaw University of Environmental and Life Sciences
Source: Polish Tyre Industry Association